Annealing form and methods



D. F. WINTER June 30, 1970 Filed June 12. 1967 June 30, 1970 0. F.WINTER 3,517,917

ANNEALING FORM AND METHODS Filed June 12. 1967 2 Sheets-Sheet FIG.3

United States Patent 3,517,917 ANNEALING FORM AND METHODS David F.Winter, Kirkwood, Mo., assignor to Central Transformer Corporation, PineBluff, Ark., a corporation of Arkansas Filed June 12, 1967, Ser. No.645,335 Int. Cl. F27b 21/04 US. Cl. 26347 6 Claims ABSTRACT OF THEDISCLOSURE An outer form for use in annealing wound type transformercores. The form is an integral one-piece open rectangular frame adaptedto receive a core such that the core yokes .or shorter core legs arerestrained against outward movement by the frame during annealing andthe longer core legs are restrained by stacking of. the core and formassemblies in an annealing oven.

BACKGROUND OF THE INVENTION This invention pertains to an annealing formand methods for producing transformer cores, and particularly to anouter form for'use in annealing wound transformer cores.

In the art of producing transformers, and particularly nealing furnaceto eliminate the stresses set up.in the cores during the winding anddie-forming operations, which stresses adversely afiect the magneticproperties thereof. After. annealing, the cores are assembled withpreformed coil units by opening them at their joints, inserting themthrough the coil centerflopenings, and

reclosing their joints. The assembled core and coil units are thenmounted by suitable frames in tanks.

Outwardly directed forces are present in the core winding both prior toand during annealing due to the tendency of the core material to relaxand return to its unpressed circular configuration. These forces tend tobow the yoke and leg portions of the core outwardly and cause the coreto assume a generally oval .or football configuration. This, of course,is undesirable since the overall core and window configuration ischanged from the desired rectangular shape having predictable dimensionsto a somewhat oblong shape having unpredictable dimensions, therebyincreasing the difliculty of lacing or assembling the core around apreformed coil unit and causing a substantial number of rejects due tothe inability of the core to be properly assembled with a preformedframe. To overcome this problem during the annealing operation, theprior art typically utilized either a plurality of band strapsencircling the core legs and yokes, or four rigid plates secured aroundthe periphery of the pore by a plurality of straps or bars. Such deviceshave not proven satisfactory, however, since they are time consuming toassemble around a core, the band straps frequently break under theexpansive loads produced during annealing, and the plates and straps areunwieldy and diflicult to use.

may be noted the provision of an outer form for wound transformer coreswhich securely restrains the cores 3,517,917 Patented June 30, 1970against outward movement during annealing and permits the cores to bemounted within the tank by preformed frames; the provision of such aform in which a core may be easily inserted and'which permits an innerannealing form to be inserted in the core window either before or afterassembly with the outer form; the provision of such a form whichsecurely restrains the inner form against rotation in the outer form;and the provision of such a form which may be utilized with cores ofdifferent sizes. In addition, the present annealing form ischaracterized by simplicity of construction, low cost and ease of use.

Other objects and features will be in part apparent and in part pointedout hereinafter. I

Briefly, an outer annealing form of this invention is comprised of anintegral one-piece open rectangular frame having a pair ofv fiat endplates held in spaced substa'ntial'parallel relationship by a pair ofside plates, one of the side plates having a center opening ofsufficient dimension for the passage of an inner annealing form. Themethod of this invention for annealing transformer cores having a pairof legs, a pair of yokes and an open center window includes the steps ofinserting the core in an outer annealing form comprised of an openrectangular frame having. a pair of plates for restraining the coreyokes against outward movement during annealing. A plurality ofassembled core and form units are then stacked with the legs of eachcore in vertical alignment so that the weight of the stack above arespective core biases the legs of that core toward each other andrestrains the legs against outward movement during an nealing. Thestacked assembled core and form units are then heated.

v BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anouter annealing form of the present invention;

FIG. 2 is a perspective view of a wound die-formed transformer core;

' FIG. 3 is a side elevation of the form of FIG. 1 with a transformercore positioned therein;

FIG. 4 is a plan view similar to FIG. 3; and

FIG. 5 is a side elevation illustrating a pair of core and 1 formassemblies stacked in an annealing furnace.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings. a

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now the drawings, andparticularly to FIG. 1, the present outer annealing form is indicatedgenerally at 1. The form is constituted by an integral one-piece castassembly defining an open rectangular frame having a pair of flat endplates 3 and 5 held in spaced parallel relationship by first and secondside plates 7 and 9, respectively. The first side plate 7 is constitutedby a pair of elongate bars 11 and 13 of generally rectangularcrosssectional configuration disposed between the upper corners of theend plates 3- and 5. Bars 11 and 13 define a center opening 15', also ofgenerally rectangular configuration, of sufficient dimension for thepassage of an inside or inner annealing form 17 (see FIG. 3). The secondside plate 9 is similarly constitutedby a pair of elongate bars 19 and21 disposed between the lower corners of end plates 3 and 5. A generallyrectangular'opening 23 is also provided between bars 1-9 and 21, and across-plate 25 spans the opening'and connects the bars at their centers.As illustrated in FIGS. 1 and 4, the cross-plate 25 is recessed belowthe inside or upper surface of bars 19 and 21, the purpose of which willbecome apparent hereinafter. A reinforcing web 27 and 29 is provided ateach of the ends 3 and 5 of the annealing form for increasing itsend-to-end strength. The webs 27 and 29 are of generally T-shapedcross-sectional configuration (see FIG. 3) having head portions 31 andshank portions 33, the head portions tapering inwardly at 35 from amaXimum width adjacent the end plates to a minimum width over the centerof the end plates. As clearly illustrated in FIG. 1, the top and bottomof the annealing form defined by the areas between end plates 3 and 5and bars 11, 19 and 13, 21 are open.

A typical wound die-formed transformer core is illustrated in FIG. 2 at37. The core is constituted by a plurality of superposed turns of grainoriented magnetic strip material die-formed into a generally rectangularconfiguration having leg portions 39 and 41 and yoke portions 43 and 45.A center generally rectangular window 47 is provided between the leg andyoke portions of the core and a series of openable joints 46 areprovided in leg 39 for permitting the core to be opened after annealingfor assembly with a preformed coil unit.

Referring to FIGS. 3 and 4, outer annealing form 1 is applied to thecore 37 after it has been formed into the configuration shown in FIG. 2,and before it is placed in the annealing furnace. To accomplish this,core 37 is placed flat on a table or suitable support such that legs 39and 41 lie in a horizontal plane. The outer form 1 is then lifted by endwebs 27 and 29, positioned above the core 37 and slipped downwardly overthe core, the latter passing through either the open top or bottom ofthe form. In this position, it should be noted that legs 39 and 41 ofthe core project outwardly from the open top and bottom of the form pastbars 11, 19 and 13, 21, and yokes 43 and 45 engage end plates 3 and 5,respectively. The assembled form and core unit is then rotated 90 on thesupport such that it rests on bars 19 and 21, and inner annealing form17 is forced through the opening '15 and into core window 47. The innercore form 17 is forced downwardly through window 47 until it abutscross-plate 25 spanning bars 19 and 21. In this position, the loweredges of the longer legs of form 17 abut the Perimeter of lower opening23 thereby holding form 17 parallel to bars 19, '21 and 11, 13 andpreventing the core from rotating in the outer form. It may be desirableto restrain core legs 39 and 41 by means of a band strap 49 encirclingthe core girth and secured by a clamp 51.

When a plurality of core and form units have been assembled, they arestacked in an annealing furnace with the legs of each core in verticalalignment so that the weight of the stack above each core acts to biasthe legs thereof toward each other, thus restraining core legs 39 and 41against outward movement. As illustrated in FIG. 5, a pair of assembledcore and form units are stacked in an annealing furnace 53 with thewindings of core legs 39 and 41 horizontal. The lower unit lies upon aheavy steel plate 55 and the units are separated by a sheet of heavygauge screen or expanded metal 57. A similar plate 59 overlies the upperunit and several additional pairs of units and .plates (not shown) arestacked in a similar manner. The uppermost plate in the stack may beweighted to provide sufficient biasing to provide restraint for the legsof the uppermost cores. Thus, the weight of the stack above a respectivecore effectively restrains legs 39 and 41 of such core 37 from outwardmovement during the annealing operation, and the outer form 1 restrainsoutward movement of the yoke portions 43 and 45. Inner form 17 maintainsthe core window 47 rectangular during annealing, and this form may beinserted in the core prior to inserting the core into the outer form,rather than after as described above.

It should be noted that each of the present outer annealing forms may beutilized with several cores of different sizes by the use of one or moreshims inserted be tween one of the core yokes and the corresponding endplate of the form. Thus, for example, only four different form sizes andeight shims are necessary to anneal cores from 8% to 14 /4 inches inlength for transformers of from 5 to 50 kva.

The outer annealing form of this invention, therefore, securelyrestrains transformer cores against outward movement during annealing,thereby holding the dimensions of these cores to close tolerances andpermitting the cores to be utilized with preformed frames ofpredetermined sizes.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. An outer annealing form for wound transformer cores, said formcomprising an integral one-piece open rectangular frame having a pair offlat end plates held in spaced substantially parallel relationship by apair of side plates, each side plate comprising two bars ofsubstantially rectangular cross-section extending between respectivecorners of the opposed end plates, one of said side plates having acenter opening of sufiicient dimension for the passage of an innerannealing form, and a cross-plate spanning the bars opposite the centeropening, said cross-plate being recessed from the inside surfaces ofsaid bars for holding an inner annealing form against rotation in saidouter annealing form.

2. An annealing form as set forth in claim 1 further comprising areinforcing web on the outside of each of said end plates, said webshaving a generally T-shaped cross-section.

3. A method of annealing wound transformer cores of generallyrectangular configuration having a pair of leg and a pair of yokeportions with an open center window therebetween, comprising the stepsof inserting the core in an outer annealing form comprised of an openrectangular frame having a first pair of plates for restraining the coreyokes against outward movement during annealing, stacking a plurality ofassembled core and form units with the leg portions of each core invertical alignment so that the weight of the stack above a respectivecore biases the legs of that core toward each other and restrains thelegs against outward movement during annealing, and heating the stackedassembled core and form units.

4. The method of claim 3 wherein said first pair of plates are held inspaced substantially parallel relationship by a second pair of plates,one of said second plates having a center opening, and furthercomprising the steps of inserting an inner annealing form through saidopening into said core window, and restraining said inner form againstrotation in said outer form.

5. A method of annealing wound transformer cores of generallyrectangular configuration having a pair of leg and a pair of yokeportions with a window therebetween, comprising the steps of insertingthe core in an outer annealing form comprised of an open rectangularframe having a first pair of flat plates held in spaced substantiallyparallel relationship by a second pair of plates, said second plateseach having a center opening therein, one of which is spanned by arecessed cross-plate, said first plates restraining the core yokesagainst outward movement during annealing, inserting an inner annealingform through said opening in one of said second plates and into the corewindow until it abuts the cross-plate, restraining said inner formagainst rotation in said outer form by engagement thereof with theperiphery of the opening spanned by said recessed cross-plate, stackinga plurality of assembled core and form units with the legs of each corein vertical alignment so that the weight of the stack above a respectivecore biases the legs of that core toward each other, thereby restrainingthe core legs against outward movement during annealing, and heating thestack ata predetermined temperature for a predetermined period of time.

6. An outer annealing form for wound transformer cores, said formcomprising an integral one-piece open rectangular frame having a pair offlat end plates held in spaced substantially parallel relationship by apair of side plates, each side plate comprising two bars ofsubstantially rectangular cross-section extending between respectivecorners of the opposed end plates, one of said side plates'having acenter opening of suflicient dimension References Cited UNITED STATESPATENTS 3,319,948 5/1967 Olsen 263-49 JOHN J. CAMBY, Primary ExaminerUNITED STATES PATENT OFFICE 69 CERTIFICATE OF CORRECTION Patent No. 3 ,5,9 7 Dated June 3 97 Inventor(g) David F- winter It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, lines 3-5, "assignor to Central Transformer Corporation, PineBluff, Ark. a corporation of Arkansas" should read assignor, by mesneassignments to Central Transformer, Inc

Pine Bluff, Ark. a corporation of Delaware Signed and sealed this 23rdday of March 1971 (SEAL) Attest:

WILLIAM E SCHUYLER, JR.

EDWARD M. FLETCHER,JR.

Commissioner of Patents Attesting Officer

